Manufacture of products of carbon



-Nov. 12; 1935.

E. BlLLlNGS :1- AL Re. 19,750

MANUFAJTURE OF PRODUCTS OF GARBONBLACK AND SIMILAR FINE POWDEBS OriginalFiled Aug. 12,. 1933 ig.'Z.

igil} Reissues! Nov. '12, 1935 19,750. MANUFACTURE OF PRODUCTS OF CARBONAND snnma BLACK FINE POWDE BS Edmund Billings, Weston, and Harold n.Oilut Winchester alaignorstoGodfreylt Cabot. Inc" Boston, Man, acorporation of Massachusetts Original No. 1,957,314; dated May 1. 1934,Serial No. 684,884, August 12, 1933. Application for reissue January 19,1935,18crial No. 2,614

1:. Claims. (cunt-5a) This invention relates to a novel product made 1from fine dry powders as a result of processes of mechanical treatmentsolely. In general it applies to the broad field of solid substanceswhich 5 derive their applications in the artsand sciences from theirfine state of sub-division. This extrerne degree of fineness carries theinevitable and, generally undesirable concomitant of dustiness, and thisdustiness, arising from the minute weight of the individual particle,may lead to serious undesirable commercial consequences; for example,contamination of other nearby products and processes, excessivedeterioration of fixtures, machinery and furnishings and respiratory andother occupational disorders in the workmen exposed to the dust.

We have discovered that certain powdered materials of this type may beagglomerated on themselves, bypurely mechanical treatment, without theassistance of binders, solvents, liquids, tars,

or the addition, either temporarily or permanently, of any foreignsubstance. The agglomerates formed by our process areof greater apparentdensity in bulk than the loose powders from which they areformed andconsist of more or less spherical masses having such a high ratio ofweight to surface that they are not dusty. Also, they have smooth,polished, non-adherent surfaces and compact, adhesive internalstructures.

These characteristics give the resulting agglomerates a free-flowingnature which materially simplifies handling in bulk, homogeneous mixingwith other materials, delivery by gravity through chutes and pipelines,packaging in any desired weight, and all of the other conveniencesimparted tothe product 'by its extreme fluidity and dustlessness.

, One important field of use for our invention isv the carbon blackindustry, for example, in

V 40 connection with the so-called "channel" carbon black produced byburning natural gas flames against metallic surfaces. The ultimatecarbon black particle is so small that its shape and exact size arebeyond microscopic determination.

As first produced, such carbon black has an apily reverts to its dustyform. In addition to this, I the diillculties of packaging carbon blackby compression have necessitated the employment of small sacks,twenty-five pounds or less in capacity, and for practical reasons theindustry has obliged to standardize on two sizes of sacks.

We have found that by subjecting the carbon I black of commerce tocertain conditions of turbulent pressure, the fine dusty particles ofwhich it is composed may be caused to adhere and ag-' glomerate firmlywith each other in groups. Thus the carbon black may be converted into10 small spherical granules of apparent density in bulk higher thanbefore such treatment, of relatively tenacious structure, with each ofsuch granules presenting a more or less polished, nonadherent surface.Carbon black in this spherill cal grain form possesses all of theadvantages of convenience in handling and distribution above discussedand, in addition, it disperses perfectly in rubber mixtures, and isotherwise as useful or more useful in rubber making and other in-' Udustries than the compressed carbon black of. commerce formerlyemployed.

Similarly we have found that a number of other fine, dry powders, amongthem, all of the carbon pigments commonly known as lamp blacks, zinc lloxide, iron oxide and clay, (previously reduced tothe requisite state ofsub-division if necessary) have the property of agglomerating underdeterminable conditions of mechanical manipulation and that whensubjected to suitable turbulent Ii pressure they may be converted intosmall, tenacious spherical granules of concentric shelled structure andhaving non-adherent surfaces.

The powders which display this behaviour have certain othercharacteristics which serve to dif- I5 ferentiate them from thosepowders which cannot be agglomeratedby such treatment. For example, ifJigged on a vibrating surface, they will agglomerate into small spheresof very fragile structure, they will form an adhesive lump whensqueezed, they will adhere to metallic or nonmetallic rods when theseare forcibly drawn through them and they are free from gummy andresinous ingredients. The present invention has to do with fine powdersor pigments having these proper- 45 ties or characteristics and forconvenience they will be termed herein as "agglomerative powders".

We hav'e discovered that by subjecting them to the. proper conditions ofturbulent pressure, and to proper manipulation these agglomerativepowders may be converted into spherical granules of greatly increasedapp rent density, having also internal structures of spherical shellsconcentrically disposed about central cores, with each granulepresenting a smooth, polished, non-adherent} and non-coherent exteriorsurface. The self-generated spherical granules thus produced a are ofappreciable mechanical strength and, since they have the property ofwithstanding very considerable direct pressure, they may be handled ortransported in bulk with practically no disintegration- The powder,converted into this spher ical-grain form, is, substantially dustless,freefiowing and non-adherent.

The proper conditions of turbulent pressure necessary for the conversionof agglomerative powders into such spherical granules may be created bythe use of various types of mechanical apparatus. One example ofsuitable apparatus is disclosed in our pending application Serial No.

642,850, filed Nov. 16,. 1932. We have found that,

under certain conditions, we can directly convert fine agglomerativepowders from their loose, seemingly amorphous form into this dense,spherical-grain form. However, the process is usually more rapid,economical and commercially efficient if a priming charge of pre-formedspherical material is mixed with the powder being treated. This primingmaterial may be either the same or different from the powder. If such apriming charge is not used, the first eifect of turbulent pressure onthe powder may be to cause the gradual formation of a small number ofnuclei consisting of a number of powder particles adherently bondedtogether. Since, in an adequate spaceof time under turbulent pressure,the nuclei as they form are pressed upon from 'all sides and in alldirections, their growth is in three equal dimensions, thus their formis spherical.

The priming charge serves at least two important purposes, i. e. (i) Itimmediately provides cores or nuclei upon which the powder may at oncebegin to adhere thus promoting or expediting formation of a largeproportion of spherical, well-agglomerated granules of low viscosity.The resulting lower average viscosity enhances the turbulent sheet ofthe mechanical apparatus used and thereby accelerates the conversionfrom powder to dustless spherical agglomerate. (2) It providesimmediately bodies of much larger weight than the weight of theparticles of dust. These larger bodies, by collision, provide impacts onthe dust particles of sufficient intensity to cause permanent adhesion.They also widen the zones of effective action in the. apparatus and sopermit the use of greater clearances than would otherwise be the case,thereby simplifying the mechanical construction of the apparatus.

There are a number of ways of producing satisfactory priming chargematerial but all are alternative methods for accomplishing two purposes;first, exerting sufiicient pressure on the powder particles to form firmadhesions; second reduction of the agglomerates thus formed to aconvenient and suitable size and with three appreciable dimensions. Forexample, satisfactory cores may be secured from some agglomerativepowders by subjecting relatively thin layers of the powders to directcompression. suificientiy heavy to cause the formation of a chunk, cakeor briquette. This, if then rubbed through a wire screen of suitablemesh, is partially disintegrated and the resulting product of thistreatment is suitable for core material and may be readily built up intospherical form by the addition of concentrlc external layers or shells.

As another example, spheres of foreign material of suitable density andsize, may be mixed with the agglomerative powder and the mixturesubjected to turbulent pressure. The powder will then form asubstantially concentric, spherical shell on each sphere. If thecomposite spherical granules thus formed are rubbed upon a screen of theproper mesh to exclude the original spheres, they will break andfragments of d 5 the shells passing through the screen will be foundsuiiiciently dense and adhesive to serve as priming material for thesubsequent agglomeration of powders of their own nature. Examples ofspheres suitable for this purpose are fine shot or seeds, such as thoseof the beet, clover or petunia.

Likewise composite granules may be formed a by using cores made from onepowder with shells formed from' an entirely different powl6 der, for usewhere a free-flowing dustless mix-. ture of two or more such powders iscommercially desired.

An important feature of our invention lies in our discovery of the factthat we are able to take these small agglomerates, which may be so fineas to partake of the characteristics of dust, and build them, throughsuccessive addition of shells, to a size that imparts to the product thecommercial advantages above discussed, viz., dustlessness, high density,low mass viscosity, spherical shape and non-adherent surface.

Another important feature of our invention lies in our discovery of thefurther fact that we can alter and control the degree of surface polishimparted to the granules since, under proper conditions, this is afunction of time of treatment.

Our ability to control the degree of surface polish enables us: 1

i-To control the viscosity of the material inbulk, thus facilitatinghandling.

2--To offset the increase in viscosity in bulk which would otherwisenaturally accompany in- 40 crease in average diameter of the individualspheres.

Thus, ability to control polish enables us to maintain adequateturbulent pressures throughout a widerange of average sphere diameterand 46 thus to add a greater number of. concentric shells and producelarger and more useful spherical agglomerates.

Since the impacts delivered by one sphere to another are a function ofthe weight of the spheres, it becomes possible to increase rapidly thedensity of the spherical granules in procass of treatment by employing apriming charge of large spheres. We may. by proper manipulation andadequate time of treatment, thus cause 5 the density of granules toapproach the absolute specific gravity of the material being treated.This is another characteristic and extremely important feature of ourinvention. I

For purposes of illustration, the invention will now be morespecifically described as carried out in connection with the productionof spherical grain carbon black. In the accompanyin draw- 1 8.

Fig. 1 represents spherical grain carbon black 05 as seen in the fieldof a microscope, magnifled 50 diameters.

Fig. 2 represents spherical grain zinc oxide, the granules being shownin cross section in the field of a microscope, magnified 60 diameters.

Figs. 3 .and 4 are sectional views of single spherical granules,magnified 300 diameters; and

Figs. 5 and 6 represent diagrammatically the conversion process ascarried out by one form of conveniently have an apparent density in bulkof more than 12 pounds per cubic foot, for example, about l8 to 20pounds per'cubic foot. The average size of these cores, as measured bysieve tests, is determined by the degrees of turbulence and pressure towhich the powder is subjected. The optimum size is determined by thenumber of concentric shell-like layers which are subsequently to beadded to the core and by the design of the apparatus in which theadditions aremade. For carbon black, an average core diameter rangingfrom 300 mesh to 60 mesh has been found satisfactory.

Substantially equal amounts of these cores and of commercial carbonblack may now be introduced into an apparatus such, for example, as

that disclosed in our pending application Serial v No. 642,850. Thisapparatus comprises a drum which constitutes a container and in whichare arranged a plurality of impelling elements and baille elementsmovable past each other in an approaching and receding manner andprovided with means to cause also an up-and-down circuation in the massdelivered thereto; The composite charge may be thus subjected topressure and to turbulence causing this pressure to be multi-directionalupon each particle thereof. This is accompanied by a sliding or'shiftingaction of the mass upon itself under conditions of pressure and astroking or polishing interaction of its particles. Under theseconditions there occurs an agglomeration of the flocculent carbon blackupon the cores or fines with the result that a s herical shell is builtup upon each core.

In Fig. 4 of the drawing is shown a core Ill upon which has been formeda concentric shell II. This figure represents a single granule ofspherical-grain carbon black at high magnification, the core being shownin elevation and the concentric shells in section.

The process may be continued until all of the flocculent carbon blackhas been agglomerated upon the cores in the form of spherical shells andif the components of the initial charges are substantially equal, it isapparent that each shell will comprise substantially 50% of the weightof the spherical grain thus formed. It'is desirable to continue theprocess for a time after the disappearance of the flocculent carbonblack from he apparatus suflicient to polish the surfaces of thespherical grains. At this stage the entire charge has been converted tospherical granules of high apparent density, the individual granulesbeing sufficiently tenacious to stand such pressures as they may besubjected to in handling, and presenting a more or less polishednon-adherent surface. If the process is continued further, the granulestend to become more and more dense and to be reduced in diameter. Theprocess may be stopped when the spherical granules have thus reached aconvenient commercial density and polish. v

We have described the production of spherical granules comprising a coreand a single concentric shell by a single regenerative processterminating when an equal weight of flocculent carbon black has beenagglomerated upon each core. If desired, a new charge of flocculentcarbon black may now be introduced into the apparatus and,

as before, this may approximateb' equal in weight the amount of thespherical grain charge already 5 produced or remaining therein. Theprocess is now renewed as before and a second concentric shellagglomerated upon the outer surface of the first. Such a second shell isindicated by reference character l2 in Fig.4 of the drawing. When theflocculent carbon black of the charge has again agglomerated, theprocess may be repeated.

In Fig. 4 a third concentric shell I3 is shown and in Fig. 2 are showngranules having as many as six concentric shells agglomerated about thecore. What has already been said applies to these additionalregenerative processes. The core and each shell is defined by a polishedor somewhat glazed spherical surface upon which the next larger shell isagglomerated and to which it directly coheres. 'I'hese'surfaces may bereadily detected as surfaces of cleavage or division in partiallycrushed or sectioned spherical granules.

Fig. 1 represents spherical-grain carbon black or of other agglomerativepowders as seen in the field of a microscope in the magnification of 50diameters. It will be noted that all the grains are spherical orsubstantially so and that there is a substantially uniform upper limitof diameter which has been attained by a large number of the granules.The smaller granules represent those which contain in their compositiona smaller number of concentric shells than the larger granules, or theshells of which are thinner.

We have found that in the case of carbon black subjected to treatment inthe type of apparatus described in our pending application Serial No.642,850, it is best to use a priming charge not coarser than 60 mesh ifan increment of equal volume is to be added in the form of a shell,because the resulting spherical grains produced by such an incrementwill then have a size of about 40 mesh and, using carbon black, we havefound that. the subjection to turbulent pressure of a charge ofspherical grain carbon black containing a substantial percentage ofgrains substantially larger than 40 mesh in the type of apparatusdescribed, results in viscosities and pressures so great as to crack andburst the granular agglomerates, thus reproducing sticky, dusty materialfrom the free-flowing, dustless charge. For this reason, when treatingcarbon black by the above process, we have found it advantageous tostart with a priming charge in the range of 150 mesh so that a largenumber of con centric shells could be added before reaching the limitingsize.

As the diameter of the spherical grains in creases with the addition tothem of successive increments of carbon black, andalso as theapplication of turbulent pressure is continued after all the flocculentcarbon black has been applied to the cores of the priming charge, someof the shells become ruptured into fragments but not into dust, andthese fragments, in the presence of their neighbors, round off andbecome to all intents and purposes new core material. Thisprocesscontinues throughout the run and results in a decrease of the averagesize of the agglomcrates with time of running. It is also to beunderstood that it is the natural tendency of all these agglomerates tobecome smaller with time of running because of increase in density dueto the impacts and pressures applied to their surfaces.

At the conclusion of the first cycle of the operation the finishedcharge may be withdrawn from the apparatus and in this conditionconstitutes a satisfactory and valuable commercial product. It.,isusually preferable, however, to sift the material at the end of eachcycle,- separating the smaller agglomerates from the mass so that theymay be used as priming material for new charges, and retaining in thefinished product only agglomerates of the larger sizes.

In the light of our present knowledge, we may suggest one theory ofwhattakes place within the drum to cause the carbon black to assume its newand relatively dense form by reference tongs. 5 and 6 of the drawing.'The stationary element '42 are arranged alternately with the movingelements 32 and the charge of black surrounds and entirely fillsthespace between these elements. As the elements 32 move relative to theelements 42 (Fig. 5), they tend to carry the black in a mass therewithbut such movement of the black is opposed by the stationary elements .2.The, result is that cones l6 and 81 of black form both forwardly andrearwardly of the elements 32 and move along with these elements, whilecones 83 and of black form both forwardly and rearwardly of the elements42 remain stationary therewith. The carbon black intermediate theelements 32 and 42 (indicated by line 90 of black particles in Fig. 5)is in a state of turbulence, the black adJacent to the elements 32moving nearly as fast as those elements and the carbon black adjacent tothe elements 2 remaining nearly stationary. The relative positions ofthe elements are constantly changing as the elements 32 approach andrecede from the elements 42 and, due to this action, the particles ofcarbon black are alternatively being brought into most intimate andbombarding relation whereby they are compacted into the relatively denseform of the finished product and into a relatively loose relation,wherein they are free to rearrange themselves for the next impact. Thusthe black particles are intermittently subjected to pressures or impactsand are relatively rearranged between the successive impacts, suchimpacts or pressures thereby becoming multi-directional, i. e. notoccurring twice in succession in the same direction.

If the cores are formed from compressed or briquetted material, we havefound it advantageous to subject the rough fragments resulting from thismethod to turbulent pressure tor a short period. This treatment breaksoil. the

rough irregular projections of such cores, tends to equalize the threedimensions, fills in the cavities with the detritus resulting from theabrasion of the projections and thus produces cores which irregular inits shape, the shell will not be perfectly spherical but will tend toapproach spherical shape more nearly than the core. In Fig. 3'

is shown a core ll of more or less irregular shape, such as mightbeifound by the compressing and breakin process, and upon this has beenformed ashell l5. Thiaitwillbenotedtendstofillin I These were displacedand lost in the operation of sectioning the spherical granules.

The limiting size of the agglomerates depends somewhat upon the designand operation of the agglomerating apparatus used for producing therequisite turbulent pressures, but is even more 15 dependentupon thenature of the agglomerative powder being treated. Zinc oxide, forexample, can be caused to agglomerate by increments into spheres oflarger than 20 mesh before the resulting increased pressure exceeds thestructural re- 20 sistance of the spherical grains and break-down intodust ensues.

The continuous tendency toward the replacement of fine material as theprocess is carried out is advantageous for two reasons:

1. It maintains the distribution of particle sizes.

2. It afi'ords a continuous replacement of fine material for the startof new cycles if these fine particles are screened out at the end ofeach run, 30 thus removing the necessity for a separate and distinctprocess or step for the production 'of cores.

The .distribution of particle sizes is important to the process forthree reasons: 3|

1. It decreases the viscosity oi the charge by providing supportingsurfaces in the interstices between the larger particles, thusincreasing the ability of the apparatus to produce adequate turbulentpressures.

2. It decreases the liability of the material to be ruptured or crushedby conveying, transportation, or handling. thus inhibiting the prematurereturnof the spherical grains to their original, dusty fine components.

3. It increases the apparent density in bulk of the commercial productover that which would obtain if only one size of particle werepresent,thus economizing on packing materials and storage space per unitweight.

While in describing the process of our invention as carried out inconnection with carbonhlack, we have suggested the addition of an equalweight of flocculent material to the priming charge, it is entirelypracticable to double this 55 proportion, that is, to add flocculentcarbon black in an amount equal to twice the weight of the primingcharge.- The percentage of priming material necessary or advisable inthe charge is a function of the combined viscosities of the prlm- 60 ingmaterial and the fine powder. From this it follows that it is possibleto use a 5% or 10% priming charge in treating certain powders, whereas a33% priming charge may be required in treating other flne powders. Inthe case of 65 carbon black, a 33% priming charge is the minimum belowwhich it is not convenient to go.

This application is, in part, a continuation of our earlierapplicationrserial No. 623,184, filed July 18, 1932, and correspondingto our Canadian 70 patent, No. 333,741, granted July 4, 1933.

' Having thus described our invention, what we claim as new and desireto secure by Letters Patent of the United States is:

1. as a new product of manufacture, carbon [6 black in the form ofspherical granules having a relatively tenacious internal structureconsisting of concentric shells of progressively increasing diametersbonded together with sufficient tenacity to withstand transportation inbulk without distintegration, the granules presenting polished exteriorsurfaces and having an apparent density in bulk of more than 12 poundsper cubic foot.

2. As a new product of manufacture, carbon black in the form ofspherical granules comprising in internal structure a central core witha plurality of concentric spherical shells enclosing the same and unitedto each other with suflicient tenacity to withstand disintegration whentransported in bulk, the granules presenting smooth, non-adherentexterior surfaces and having an apparent density in bulk of at least 18pounds per cubic "foot.

3. As a manufactured product, carbon black in the form of sphericalgranules between 300 mesh and 20 mesh in diameterJof more than 12 poundsper cubic foot in apparent density and each comprising adense compactcore surrounded by a spherical shell of substantially the same densityas the core and built up progressively upon the core by the applicationof turbulent pressure to flocculent carbon black with sufficientcohesiveness to maintain its identity and adapt the granules towithstand disintegration when transported in bulk and presenting asmooth, non-adherent exterior surface.

4. As a manufactured product, carbon black in the form of sphericalgranules each comprising an integral coherent core surrounded by aseries of concentric shells of substantially equal density,

, each sumciently cohesive to maintain its identity when the granule iscut in cross section, presenting a spherical exterior light-reflectingsurface and being tenaciously bonded with the core sumciently towithstand disintegration when trans-,

ported in bulk.

5. A new product of manufacture, consisting of carbon black in the formof solid spherical granules between ,300 mesh and 20 mesh in diameter,

having hard, impact-formed, non-adherent surfaces and a compact, densestructure of pure carbon black particles built up systematically andprogressively by application of turbulent pressure to floccuient carbonblack, the particles being united only-by their own cohesive force withsumcient tenacity of structure to'resist disintegration when in bulk,and having 'csrbonblschandhsvinganapparentdensityof more than 12 poundsper cubic foot.

'hA new product of manufactm'e, consisting of carbon black in, theform'of substantially spherical granules between 300 mesh and 20mesbindiametensndfrsgmentsof nichsphesical granules, said sphericalgranules having polished non-adherent surfaces. an apparentdensityofnotlessthsnlzpoimdspercubicfootandaeompsctdenseinternalstruotureofpurecarbon blaekparticles arrangedsystematically in forcible engagement with each other by turbulentpressure and maintained by their own cohesive force with such tenacityof structure as to withstand disintegration when transported in bulk.

8. As a new product of manufacture, fine dry 5 agglomerative powder inthe form of solid, tenacious, substantially spherical granules not over20-mesh in diameter and comprising in their internal structure distinctconcentric shells of progressively increasing diameter bonded togetheronly by the impact-generated cohesion of the particles of the powder,the granules presenting polished exterior surfaces and being adapted byreason of their structure to withstand transportation in bulk withoutdisintegration.

9. As a new product of manufacture, fine dry agglomerative powder in theform of solid, substantially spherical granules comprising in theirinternal structure concentric shells, each intact, of substantiallyequal density and bonded togeth- 20 er only by the impact-generatedcohesion .of the particles of the powder with sufiicient tenacity towithstand the pressure of transportation in bulk without substantialdisintegration and presenting a polished, non-adherent exterior surface.

10. As a new product of manufacture, flne dry agglomerative powder inthe form of solid, substantially spherical granules'of suflicientmechanical strength to withstand disintegration when handled in bulk andof greater apparent density than the loose powder, each granulecomprising a series oi distinct impact-formed concentric shells unitedin an integral body only by the impact-generated cohesion of theparticles of the powder and presenting a smooth non-adher- .15 entsurface.

11. A new product of manufacture, consisting ing of fine dryagglomerative powder in the form of solid, substantially sphericalgranules between BOO-mesh and 20-mesh in diameter, having hard 40 drypowder, the particles being united only by their'own cohesive force withsuflicient tenacity of structure to resist disintegration whentransported in bulk, and having an apparent density .in bulk greaterthan that of the powder.

12. As a manufactured product, a fine dry pow- 60 der of zinc oxideagglomerated in the form of spherical granules having an internalstructure sufficiently tenacious to withstand disintegration whenhandledin bulk and consisting of a substantiaily spherical core and aconcentric shell built up progressively and systematically by theapplication of turbulent pressure to the zinc oxide powder and unitedthereto by impact-generated cohesion of the zinc oxide particles andpresenting a polished exterior surface.

13. As a-manufactured product, a fine dry powder of, zinc oxideagglomerated in the form of solid spherical granules between 300-meshand 20- mesh indiameter and each having a smooth impact-formednon-adherent surface and a dense so sturdy structure built upprogressively and systematically by the application of turbulentpressure to the free dry powder of zinc oxide and having an apparentdensity of more than 20 pounds per cubic foot. l0

. EDMUND BILLINGS. 1

HAROLD H. OFFU'IT.

